1. Field of the Invention
The invention relates to an angled gas conduit for a high pressure and high temperature gas flowing at a high velocity. More particularly, the invention concerns a device for the connection of the hot gas collector space of a gas cooled high temperature reactor with a component of the cooling gas circuit. The angled gas conduit may also be equipped with internal insulation.
2. Background of the Prior Art
It is well known in the art to separate the part of a gas cooled nuclear reactor installation containing the core of the reactor from the part containing components of the primary circuit, such as for example steam generators housed in common pressure vessels by means of shielding devices. This prevents the activation of these components by direct neutron irradiation. Furthermore, measures are known to permit the cooling gas to flow without appreciable drop in pressure from the reactor core to the components of the primary circuit, without the passage of harmful radiation through the free cross section of the gas conduit connecting the reactor core with the components.
In West German Published Application No. 10 83 945, a reactor core shield is described, comprising a cylindrical inner piece and an external shielding annulus, which together with a further shielding annulus forms an S-shaped flow path for the cooling medium. This shielding device requires a great expenditure of material.
In West German Offenlegungsschrift No. 1 464 705 a tubular conduit is described. The tubular conduit emerges from the reactor core. It displays an expanded part in the area of its passage through the reactor container. A shielding block is built into this expanded part. The shielding block covers the cross section of the conduit and the flow of gas or fluid is conducted around the shielding block. This type of shielding has the disadvantage that the cross section of the conduit must be enlarged in the area of the shielding block.
In West German Offenlegungsschrift No. 2 257 699, a bent piece of tubular conduit of relatively large diameter for a rapidly flowing medium is described. A lattice of blades is installed at the location of the bend in order to improve the flow profile.
Arrangements to improve the mixing of the hot cooling gas in a nuclear reactor have been proposed. These, however, are arranged within the hot gas collector space located beneath the core of the reactor and effect the equalization of the temperature profile prior to the entry of the flow of gas into the hot gas conduits.
One of these arrangements consists of a V-shaped displacement body installed in front of each hot gas conduit on the floor of the hot gas collector space. The displacement bodies are intended to direct the flow of the hot gas upwards.
In the case of another installation, satisfactory mixing of the hot cooling gas is obtained by arranging round columns in the hot gas collector space and supporting the bottom reflector. These are in the form of hollow columns. The inner space of the hollow columns is connected on the one hand by means of radial bores with the hot gas collector and is in communication on the other hand with cooling gas passages in the bottom reflector.
In addition to other measures, it is customary to bend the gas conduit following its passage through a shielding wall, i.e. to use an angled gas conduit. The conduit may be bent as much as 90.degree. in known reactor arrangements.
This is true, for example, in the base of THTR-300 MWe, wherein the gas heated in the core of the reactor is collected in a hot gas collector space and conducted through respective gas conduits to the steam generators. The gas conduits initially pass horizontally through the thermal shield and are then bent upwards at an angle of 90.degree. so that they may be connected with the jacket of one of the steam generators.
In such gas conduits, the deflection of the flow of gas in the angled section of the gas conduit leads to the establishment of nonuniform velocity and temperature distributions. The first results in unfavorable inflow conditions in the reactor component attached to the gas conduit, subsequently leading to overstressing and, thus to the destruction of parts in the lower areas of this component. Non-uniform temperature profiles create hot strands of differing temperatures in the flow of gas, which must again be avoided.